The present invention relates to a recording/reproducing optical disk, in which data recording/reproduction can be conducted by use of a sector disposed along a spiral track as a unit, and to an optical disk reproducing apparatus for data recording/reproducing on the optical disk.
Heretofore, rewritable optical disks available on the market have included optical disks having diameters of 120 mm and 90 mm and phase change disk of 120 mm in diameter (popular as PD).
These disks comprise guiding grooves for laser light illumination. Tracking is carried out by analyzing laser light based on the guiding grooves. The guiding grooves are formed as a continuous spiral which runs from the inner side of the disk to the outer side thereof. Heretofore, the guiding grooves each are referred to simply as "a groove" and a portion other than the grooves are referred to as "a land." In a conventional optical disk, information has been recorded either in a groove or on a land.
Such information on an optical disk is read and written for example, in 512 bytes or 2048 bytes as a unit. This information unit is called "a sector." In this sector, a sector address which indicates a location of the sector is assigned and formatting is conducted according a predetermined sector format in order to record information to a target address and to reproduce the information with high reliability. In the formatting, information on a sector is recorded by forming a recess/protrusion profile called "a pit" at a head of the sector. This portion in which the sector address information is recorded is called "a header." In a conventional optical disk, as described above, since information has been recorded in either a groove or a land, the header must be either in a groove for groove recording, or on a land for land recording.
While a conventional optical disk has recorded information either in a groove or on a land as described above, the recording capacity of the disk can easily be increased if information is recorded on both the groove and the land.
However, a problem arises regarding formatting the sector address in a manner such that information can be recorded in both the land and the groove.
In a conventional optical disk provided with a spiral groove as described above, the groove and the land are formed parallel to each other, hereinafter referred to as a double spiral structure.
In a double spiral structure, since grooves and lands are formed in parallel to each other, travel from a groove to a land requires a track jump. Therefore, whenever recording/reproducing of information is switched from a groove to a land and vice versa, a track jump or a seek is necessary, thereby making continuous recording/reproducing of information difficult.
Additionally, the only way to manufacture a disk in the double spiral format, is to separately format a sector in a groove (hereinafter referred to as groove sector) and another sector on a land (hereinafter referred to as land sector). Thus, it becomes difficult to format a disk, for example by a zone CAV format, so that recording/producing of information can alternately be conducted on a land or in a groove adjacent to each other.
That is, in order for a land and a groove adjacent to each other, to have sector addresses numbered in a continuous manner, either the grooves or lands must be independently formatted, while being separately assigned with addresses in an intermittent manner. In this case, unless travel from a land to a groove or vice versa is smoothly performed, disk rotational delay time occurs, which causes a problem of interference with realization of continuous recording/reproducing of information.
In addition, its desirable to achieve as much distance between pits in a header as possible in order to perform a more stable reading of the header.